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Research Round-up on Vitamins and Minerals

29 October 2012

In the long-running search for ways to make better use of dwindling world resources of phosphates for poultry diets, a review of recent research reveals that phosphorus and calcium levels can be reduced in broiler diets without compromising performance and that copper source can impact phosphorus retention by hens. Folic acid has been shown to affect the immune response, which may help in future to reduce the routine use of antibiotics in feeds, and light has been shed on a possible new role for vitamin E in improving chicken meat quality.

Phosphorus Interactions in Broilers Studied

Reducing phosphorus and calcium levels during broiler rearing can be achieved without compromising broiler growth or bone development in research from Belgium, while retention of calcium and phosphorus were improved.

The consequences of phosphorus interactions with calcium, phytase and cholecalciferol (a precursor of vitamin D) on broiler performance and mineral retention have been studied by researchers at the Institute for Agricultural and Fisheries Research (ILVO) in Melle, Belgium.

Reporting their work in Poultry Science, Evelyne Delezie1 and colleagues explain that their objective was to determine the effect of calcium, total phosphorus, cholecalciferol and phytase level in the diet on the performance, tibia ash percentage and calcium and phosphorus retention in broilers until slaughter age.

Broilers were randomly assigned to 12 treatments, each with six replicates, comprising three diets differing in calcium and phosphorus level:

normal calcium and total phosphorus level (NN)

normal calcium and low total phosphorus level (NL)

low calcium and total phosphorus level (LL).

Broilers were also given two levels of cholecalciferol and two levels of phytase.

The normal levels of calcium and total phosphorus for the starter, grower, and finisher phases were 0.90, 0.82, 0.74 per cent and 0.67, 0.62, 0.57 per cent, respectively. The low calcium and total phosphorus levels for the three phases were 0.67, 0.60, 0.52 per cent and 0.57, 0.51, 0.46 per cent, respectively.

Broilers of the NL treatment attained the lowest bodyweight, whereas the bodyweights of the NN and LL groups were comparable. Cholecalciferol significantly affected the bodyweight, with differences up to 2.6 and 1.2 per cent for the starter and grower phases, respectively. The highest cholecalciferol effect was found in combination with the NN treatment.

The percentage of retained calcium increased from 33 per cent to 41 per cent and 48 per cent when the imbalanced diet was replaced by the NN and LL balanced diets, respectively.

Phosphorus release from phytate was 64 and 67 per cent for the NL and LL diets, respectively. Phytase and cholecalciferol had significantly favourable effects on retention values but these effects were dependent on calcium and total phosphorus levels and their ratio.

Both diets with the balanced calcium/total phosphorus ratio resulted in the best performance, highest tibia ash percentage and phosphorus release from phytate, concluded Delezie and colleagues. A reduction of the Aviagen (2009) recommended phosphorus requirements by 25 to 30 per cent and calcium by 15 to 20 per cent over the various phases did not negatively affect performance or bone development in this work, and improved calcium and total phosphorus retention. The effects of supplementing cholecalciferol and phytase were additive but not significant and no synergy was observed between these additives.

Copper Source Affects Phosphorus Retention in Hens

The influence of different dietary copper sources on eggshell quality and phosphorus retention in laying hens were investigated by researchers based at Istanbul University in Turkey. There were no effects on the eggshell but one of the copper sources, combined with the low-phosphorus diet and added phytase enzyme, reduced the retention of phosphorus by the young hens.

Writing in the Journal of Applied Poultry Research, A.Y. Pekel2 and colleagues at Istanbul, together with a co-author from The Pennsylvania State University in the US, assessed the effects of dietary supplementation with phytase and prophylactic levels (250mg/kg) of copper (Cu) from various sources (inorganic Cu sulphate versus organic sources, Cu lysine and Cu proteinate) on eggshell quality and phosphorus retention of layers that were fed low-phosphorus diets (0.11 per cent available phosphorus).

In the first experiment, 120 Lohmann Brown hens, 40 weeks of age, were assigned to one of five dietary treatments to evaluate eggshell quality (eight replicates per treatment and three birds per replice). At 45 weeks of age, eight chickens in each treatment were placed in metabolic cages individually and subjected to the same treatments as in experiment 1 to determine phosphorus retention.

No significant differences were observed among the treatments in terms of eggshell thickness, eggshell weight, percentage of damaged eggs, and specific gravity at the end of the first experiment. Feed consumption of the hens fed the Cu lysine diets was significantly lower than hens fed diets that were not supplemented with copper and those fed diets supplemented with Cu proteinate in the second experiment. The inclusion of phytase to a low-phosphorus diet effectively supported and allowed almost the same eggshell quality and phosphorus retention compared with the high-phosphorus diet (0.24 per cent available phosphorus).

Feeding diets low in phosphorus together with 300 units of phytase and copper from three different sources in the current experiment did not result in any decrease in eggshell quality. However, the use of supplementary copper to provide 250ppm from Cu lysine in low-phosphorus diets plus 300 units of phytase decreased phosphorus retention.

Effects of Folic Acid on Immune Response Investigated

Canadian researchers have investigated the effects of the water-soluble vitamin, folic acid on the immune response of young hens, and they were able to identify some significant positive effects.

In a paper published in Poultry Science, P.M. Munyaka3 and colleagues at the University of Manitoba in Canada explain that they investigated the effects of dietary folic acid supplementation on immunological parameters in young laying hens under acute conditions of lipopolysaccharide (LPS) challenge.

Twenty-four Shaver White laying hens at 24 weeks of age were fed two diets in a completely randomised design. The diets were wheat-soybean based, with either 0 or 4mg of supplemental folic acid per kilogram of diet. At 32 weeks of age, six hens from each dietary treatment were injected intravenously with 8mg kg bodyweight of either LPS or saline. Four hours after injection, blood was collected and the hens were euthanised to obtain spleen and caecal tonsils.

Heterophil:lymphocyte ratio, CD3+, CD4+, CD8+ T cells, and CD4+:CD8+ cells in the blood and spleen were not affected by dietary FA. Relative to saline-injected hens, LPS-injected hens had fewer CD3+, CD4+, CD8+, and CD4+:CD8+ cells in the blood, and no difference was found in the spleen.

Total protein, albumin and globulin were found to be higher in folic acid-supplemented hens than the control. However, total protein, albumin, and globulins decreased in the LPS-injected hens compared with the saline control.

Expression of interleukin (IL)-1Β in caecal tonsils decreased in folic acid-supplemented hens but no dietary influence was found on the expression of other genes in both the spleen and caecal tonsils.

Lipopolysaccharide up-regulated expression of IL-10 and interferon (IFN)-γ in the spleen, and IL-1Β, IL-10, and IFN-γ in the cecal tonsils, whereas the expression of Toll-like receptor (TLR)-4 and IL-8 was not influenced by LPS in the spleen and caecal tonsils.

There was a diet × challenge interaction for total IgG, and cytokines IL-1Β and IL-18 in the spleen as well as IL-18 in the caecal tonsils, according to Manyuka and colleagues. They concluded that there were few interactions of dietary folic acid and LPS. However, folic acid increased biochemical constituents, enhanced generation of total IgG and exhibited pleoitropic effects in inflammatory responses.

Extra Vitamin E for Broilers Helps Prevent Nutritional Myopathy

Additional vitamin E in the diet of broilers had some effects on reducing nutritional myopathy, a condition that reduces chicken meat quality, according to new research from Canada.

Nutritional myopathy in broiler chickens is a condition that is generally asymptomatic but leads to a loss of meat quality, according to B. Guetchom4 at the Faculty of Veterinary Medicine in Saint-Hyacinthe, Quebec, Canada and co-authors there and at Couvoir Scott and Quebec's ministry of agriculture (MAPAQ). According to their paper in Journal of Applied Poultry Research, this condition could sometimes be associated with suboptimal or deficient levels of vitamin E in the diet.

The objectives of this study were to assess the effect of extra dietary vitamin E in a commercial diet on muscle integrity and to determine an efficient diagnostic test for early detection of muscle damage, subsequently to adjust vitamin E levels in the diet.

One-day-old male broiler chicks were randomly assigned to two dietary treatments: a commercial diet in which up to 50mg per kg of vitamin E was added, or a commercial diet without extra vitamin E.

On days 28, 35, 42 and 49, blood samples were taken to measure plasma vitamin E and creatine kinase (CK) activity. Both pectoralis superficialis and adductor magnus muscles were sampled for histological examination, and degenerated fibres were counted.

Plasma levels of vitamin E were higher in chickens from the test group, whereas creatine kinase activity was not different between the groups. Fewer damaged fibres were observed in the pectoral muscle at 28 days in chickens receiving the diet supplemented with extra vitamin E.

Guetchom and co-authors concluded that adding vitamin E to a conventional diet increased plasma vitamin E and mildly decreased the number of damaged fibres in the pectoral muscle of young broilers. They remarked that blood creatine kinase activity was not a reliable biochemical indicator of mild muscle degeneration in broiler chickens.